1. Technical Field
The present invention relates to a jigsaw in which a saw blade is caused to reciprocate in an up-and-down direction by a motor and a workpiece, such as timber, is cut while a main body is forcedly pushed forward, and more specifically, to a mechanism that reciprocates a saw blade even in the front-and-rear direction.
2. Description of Related Art
A jigsaw in which a saw blade is caused to reciprocate in an up-and-down direction by a motor and a workpiece, such as timber, is cut while a main body is forcedly pushed forward, is much used for cutting boards in housing construction using a 2×4 construction method. It is known that this jigsaw is advantageously adapted to reciprocate a saw blade not only in an up-and-down direction but also in a front-and-rear direction so as to draw an elliptical locus.
For example, four types of loci of a saw blade including Routes 1 to 4 are shown in FIG. 5 of JP-A-53-117897(Patent Document 1). Among these, Route 1 is shown in FIG. 6. The specification of Patent Document 1 describes “The contour of Route 1 provides particularly good cutting properties. Specifically, a saw blade engages a workpiece over almost the whole upstroke ranging from Point 1 to Point 11. Then, at Point 11, the saw blade moves to Point 1 through Point 12/0, and thereby the saw blade is withdrawn from cutting engagement to provide space enough to remove chips before it moves down to Point 6.”
In addition, according to JP-A-53-117867, the jigsaw is expensive since it is difficult to form the cam. A formation of the cam is difficult, so that the saw blade does not smoothly change to follow an excursion thereof.
However, even in the jigsaw in which the saw blade is adapted to draw such a locus, if the force that an operator pushes the main body forward is strong, there is a case that the main body advances more than that until the saw blade reaches Point 12/0 and the saw blade does not yet separate from a surface to be cut even when it has reached Point 12/0.
While the saw blade ascends by a frictional force acting between the saw blade and the surface to be cut, the main body is pushed down, and at a moment when the saw blade reaches the uppermost point so that it may be switched to descent, the main body is opened from the push-down force, and is now strongly pushed up. This instantaneous change in the direction of force causes large vibration of the main body. Further, since prompt descent of the saw blade is hindered, the cutting speed may be lowered.